1. Field of the Invention
The present invention relates to a device for feeding pressurized liquid to a hydraulic circuit of a machine which comprises a hydraulic actuation element. For the description of a machine which comprises a hydraulic actuation element and a hydraulic circuit suitable for being fed by the device according to the invention, reference is made to the hydraulic press described in the PCT patent application no. PCT/EP 89/00610. The term "liquid" is used herein to generally refer to hydraulic oil, emulsions thereof, or to other liquids suitable for being used in hydraulic circuits for the actuation of hydraulic actuation elements.
The field of the present invention relates to devices which comprise a motor, a flywheel mounted on a shaft, a positive-displacement pump mounted on said shaft, a flywheel containment and supporting structure, and a motion transmission element suitable for transmitting the motion from said motor to said shaft.
The positive-displacement pump generally operates at rather high pressures, in excess of 100 bar, often higher than 200 bar, with peaks of over 300 bar. The momentary power transmitted from the flywheel to the pump is very high, up to 300-400 kw.
The above is in summary the main field of industrial use of the invention, but does not constitute a limitation of the scope thereof, since the device according to the invention, in particular as hereinafter described and claimed, can be advantageously used in any other equivalent field in which it is necessary to feed pressurized liquid, at a variable pressure during the working cycle, and in particular when it is necessary to transmit an extremely high momentary power.
2. Description of the Prior Art
Devices of this type are known and are described for example in the PCT patent no. PCT/EP 89/00610 in the name of the same Applicant, wherein the shaft on which the Dump and the flywheel are mounted is the motor shaft and said shaft is supported by the internal bearings of the motor.
Said known devices, however, entail some problems, since it is obviously impossible to mount more than one pump for each flywheel, and the containment of all the kinetic energy stored in the flywheel is entrusted exclusively to the bearings of the motor, which have not been designed for this purpose. It is furthermore difficult to try to mount further additional bearings, due to problems of coaxiality with the motor shaft. In view of the fact that the flywheel rotates at approximately 1800 rpm for these applications, it can be easily predicted that safety problems arise, especially in cases in which large flywheels are required. A vault-shaped structure, arranged over the flywheel, in order to protect the surrounding area, is in fact generally provided due to safety problems.
Japanese patent applications JP-A-56-111593 and JP-A-56-111594 describe a supporting structure of a flywheel connected with a pump group by an electromagnetic clutch.
This arrangement gives rise to some problems: an electromagnetic clutch can only transmit a limited power and is a complex device which can easily break under heavy loads; furthermore some of the energy generated by the flywheel is lost and is converted into heat for the friction inside the clutch. It is impossible to use standard pumps, since the described twin pumps require a special manufacture. The centering of the seats of the pump and of the bearings of the flywheel is complex and requires a long and expensive working process.
U.S. Pat. No. 3,756,751 describes a clutch housing in which a hydraulic pump is connected with a flywheel by gears. This solution cannot of course transmit high momentary power, since only the power sustained by the gears can be transmitted.
Canadian patent No 1144784 describes some housings for flywheels, but does not disclose anything about the connection with a pump.